A naval radar system typically searches space under control of command and decision processing. It searches by means of a plurality of sequential directional beams which may be pointed in a given direction. Command and Decision determines the acquisition face to be searched. The acquisition face can be calculated using the azimuth and elevation centers and extents, among other data. The radar beam is directed to each angle so as to cover the entire search face. This type of searching is subject to time constraints, as the beam typically dwells at the current beam angle for a sufficient time for the transmitted radar signals or pulses to travel to the target, which might be at the maximum allowable range, and for the reflection to return to the radar. The round-trip time is the well-know 12.4 microseconds per mile of target range. Thus, the beam dwells at each angle of the search face for a sufficient length of time to detect a target at the maximum range, and then move on to the next angle within the search beam pattern.
The angular area covered by a single radar beam is typically smaller than an acquisition face. Each beam is sufficient to search the area it covers between the range limits of the search volume. Therefore to search the volume, a pattern of sequential beams can be sufficient to cover the acquisition face.
To keep the radar system in use, as when searching multiple volumes in the case of multiple potential targets, it is typical to limit the amount of time spent searching a given volume. Because the radar may have multiple, equal priority tasks, the radar time/usage is scheduled. The radar may have to search multiple volumes and provide updates on the positions of detected targets. The system aborts the search of a volume of space after a given time. Consequently, a search through a volume of space may be initiated and aborted without being completed. This operation may result in a failure to locate a target within the specified scan volume. In order to avoid having a scan aborted and the resulting problems, it is useful that the searching of any given volume be performed in the least possible time.
The naval radar system can operate in a volume search mode. When information becomes available from another source, such as a cooperating radar, about the possible presence of a target in a nominal given direction or location, it may be desired to examine a volume about the nominal given direction in an attempt to acquire the target. This is termed a “cued” search. If the selected volume is too large, the search may time-out before completion of the search, and if too small, may not find the relevant target(s).
Improved or alternative arrangements are desired for establishing the angular extent of the search volume about the cued nominal direction of a target to guarantee that the search can be accomplished within given time constraints.